Hi,
Since none of the SGP comes with ICS and after I lost my SGP 4, I think I like to have the built-in encryption of ICS.

Does the Samsung Galaxy S2 running ICS do everything the SGP 4 does? If yes, I don't really care about the phone, I will just get a Galaxy S2 instead of getting another SGP 4. Does this make sense? Does the S2 do everything the SGP 4 does, without a service plan?

As far as I can tell, yes. Android is pretty much always still android, the only conceivable difference is custom applications. I don't own either device so I can't do a side by side for you. Were there any custom applications from the manufacturer on the SGP 4 that you can't live without?

You might also consider the samsung galaxy nexus phone since it has better screen resolution (at the cost of less battery life and no microSD card)

Ok, I eventually got a brand new Samsung Galaxy S2 from Walmart for US$300+tax. Then I activated with a $30/month prepaid plan for 100 min voice and unlimited web data. It came with ICS 4.0.4. I love it.

Ok, I eventually got a brand new Samsung Galaxy S2 from Walmart for US$300+tax. Then I activated with a $30/month prepaid plan for 100 min voice and unlimited web data. It came with ICS 4.0.4. I love it.

Congratulations! I too just picked one up (new, no contract, from eBay) The model at Walmart for $300 is an excellent price for no-contract. Even if someone were to buy it and NOT activate it, it makes a top notch portable media player.

I highly recommend getting UberPlayer from the Google play store (along with the free Zune skin). A terrific music player that looks beautiful on the SGS2. (but then again, I'm still a Zune fan and regularly use a 16GB Zune HD)